The Winter Environmental Continuum of Two Watersheds

Abstract

This paper examines the winter ecosystemic behavior of two distinct watersheds. In cold-temperate regions, the hydrological signal and environmental parameters can fluctuate dramatically over short periods of time, causing major impacts to aquatic habitats. This paper presents the results of the 2011-2012 winter field campaign in streams and rivers near Quebec City, QC, Canada. The objective was to quantify water quantity and quality parameters and their environmental connectivity from headwater creeks above to the larger rivers below over the entire freeze-up, midwinter and breakup periods with a view toward exploring the watershed continuum. The paper presents how aquatic pulses (water level, discharge, temperature, conductivity, dissolved oxygen and turbidity, measured at seven sites on an hourly basis along channels of different sizes and orders) evolve through the aquatic environment. Ice conditions and the areal ice coverage were also evaluated (on a daily time step along each instrumented channel). Some findings of the investigation revealed that water temperatures remained well above 0 • C during winter in headwater channels, that dissolved oxygen levels during winter were relatively high, but with severe depletions prior to and during breakup in specific settings, that high conductivity spikes occurred during runoff events, that annual turbidity extremes were measured in the presence of ice and that dynamic ice cover breakup events have the potential to generate direct or indirect mortality among aquatic species and to dislodge the largest rocks in the channel. The authors believe that the environmental impact of a number of winter fluvial processes needs to be further investigated, and the relative significance of the winter period in the annual environmental cycle should be given additional attention.

River and Lake Ice Processes—Impacts of Freshwater Ice on Aquatic Ecosystems in a Changing Globe

“…Climate change effects must be viewed through a regional lens, understanding the specific types of changes in precipitation, temperature, wind, and other variables that may occur, and building an understanding of how that will affect the ecosystems in a region. To help build the necessary local-regional-global understanding, synthetic work to understand differences across watersheds, across lakes, across rivers, and across regions such as those already presented here [32,62,64] and elsewhere [3,9] is very valuable-identifying common responses of ecosystems through winter, and differences across regions, and across types of lakes and rivers. This type of comparative approach will help to build a more diverse, regionally-informed understanding of physical, hydrological, hydraulic, biogeochemical, and ecological change, particularly when coupled with work to inform process-based understanding of changes through winter (e.g., [10,12]), and to integrate our growing understanding of winter changes into model-based frameworks (e.g., [76][77][78]).…”

“…Winter changes span many more variables. Turcotte and Morse [64] studied the impact of ice breakup on peaks in specific conductivity and turbidity using a conceptual model, the winter environment continuum, to help relate the winter conditions in headwater streams to the water quality state along the river network during the winter. This linking of physical and chemical change is a key area for additional work across lentic and lotic environments.…”

The Ecology of River Ice

“…rivers differ substantially from that of large rivers and the way ice forms is highly dependent on channel gradient, channel morphology, and weather characteristics such as the amount and type of precipitation (Buffin-Bélanger et al, 2013;Turcotte & Morse, 2013;Turcotte et al, 2012). In general, smaller rivers tend to have a wider range of ice types than large rivers (e.g., anchor ice-Figure 1c, suspended ice cover and ice shells-Figure 1e, solid ice coverage, floating ice), due to variation in channel morphology (e.g., presence of woody debris dams) and degree of warming from groundwater (Turcotte & Morse, 2017;Turcotte et al, 2014a).…”

Spatial variation of flow characteristics in a subarctic meandering river in ice‐covered and open‐channel conditions: A 2D hydrodynamic modelling approach

“…In addition, ice cover has been also observed to reduce turbidities when compared to the open‐channel conditions of equivalent discharges (Kämäri et al, , ). However, Turcotte and Morse () have observed both lower or higher turbidities in ice‐covered channels than in open‐channel conditions. While the spring snow‐melt flood and ice breakup periods may be major sediment transport events and may also be when the greatest annual turbidities occur (Turcotte et al, ; Turcotte and Morse, ), the other seasons (including mid‐winter, where there are ice‐covered low flows) may cause great total channel changes (Lotsari et al, ).…”

“…However, Turcotte and Morse () have observed both lower or higher turbidities in ice‐covered channels than in open‐channel conditions. While the spring snow‐melt flood and ice breakup periods may be major sediment transport events and may also be when the greatest annual turbidities occur (Turcotte et al, ; Turcotte and Morse, ), the other seasons (including mid‐winter, where there are ice‐covered low flows) may cause great total channel changes (Lotsari et al, ). In subarctic sand‐/gravel‐bed rivers, earlier studies have shown the whole open‐channel low flow period (i.e.…”